1. 标准的rownum分页查询使用方法：

select *
  from (select c.*, rownum rn from content c)
 where rn >= 1
   and rn <= 5

2. 但是如果, 加上order by addtime 排序则数据显示不正确

select *
  from (select c.*, rownum rn from content c order by addtime)
 where rn >= 1
   and rn <= 5

解决方法，再加一层查询，则可以解决，

select *
  from (select rownum rn, t.*
          from (select title, addtime from content order by addtime desc) t)
 where rn >= 1
   and rn <= 5

如果要考虑到效率的问题，上面的还可以优化成（主要两者区别）

select *
  from (select rownum rn, t.*
          from (select title, addtime from content order by addtime desc) t
         where rownum <= 10)
 where rn >= 3